1. Field of the Invention
The invention relates to the field of register display mechanisms, and more particularly to a mechanical display of the odometer decade counter type which can be operated in both forward and reverse directions with positive indexing of the digits being displayed by the register.
2. Description of the Prior Art
Many utility meters utilize odometer-type decade counters in order to display the quantity of a commodity (e.g. gas, water or electricity) being measured by the meter. These registers take the form of a decade counter having one or more register display wheels mounted side by side along a common axis. The least significant digit wheel (generally the rightmost wheel on the display) is connected to a gear train which is turned by the measuring mechanism of the meter. The least significant digit wheel is connected to the next most significant digit wheel by a simple escapement mechanism. Decade counters of this type are well-known and their operation and construction will not be described in further detail.
Conventional odometer-type decade counter register display mechanisms include some sort of "roll-back" prevention mechanism which allows the register wheels to rotate in only one direction (e.g. from lower quantities to higher quantities). This anti-"roll-back" mechanism conventionally takes the form of a one-way escapement mechanism comprising an asymmetrical cam and spring-loaded "catch" or pin. The anti-"roll-back" mechanism is employed to ensure that the meter cannot be tampered with, and specifically to prevent the amount being display from being reset to a lower quantity. However, under current regulatory schemes in force in some jurisdictions, it is now necessary for a meter to measure the flow of water or gas or electricity bi-directionally, i.e. into or out of the metering mechanism. For example, in some jurisdictions, a consumer who generates his own electricity (so-called co-generation) may pass it back to the electrical utility and receive a credit for the amount so transferred. A conventional one-way register mechanism with roll-back prevention is incapable of showing the net transfer of such a commodity.
An additional feature of modern meter register display mechanisms is the inclusion of electronic encoders which enable the position of the various register display wheels, and hence the displayed reading, to be remotely read. For example, U.S. Pat. No. 4,085,287 for "Data Transmitter for Remote Meter Reading" discloses a system for remotely reading an encoded water meter register of the type described above. One or more of the register display wheels have a small circuit board arranged next to them. Each circuit board has a series of electrical contacts arranged in a circle next to the display wheel. The display wheel carries an electrical wiper or contact arm. When energized, the position of the wiper arm on one of the contacts indicates the position of the register wheel and thus the digit being displayed.
One problem associated with the type of register shown in U.S. Pat. No. 4,085,287 is that if the position of the register display wheel is between two display positions, (e.g. it is between two displayed numbers) the reading being taken by the remote meter reading equipment will be ambiguous. This means that the meter reader will have to wait until more water has passed through the meter sufficient to move the register wheel into an unambiguous display position.
In order to overcome this problem, it has been proposed to utilize the repulsive effect of two magnets having like poles disposed opposite each other, one on the register display wheel and the other mounted at a fixed position adjacent the register display wheel. The interaction of the two like magnetic poles when they pass adjacent each other causes the register wheel to "snap-over" and move to the next adjacent position. Unfortunately, the arrangement is relatively costly due to the use of the two magnetic components. Furthermore, the use of a magnet on the register display wheel causes it to become unbalanced, thus affecting the accuracy of the displayed reading. Furthermore, the magnetic assembly could be tampered with or defeated with the use of a large magnet placed nearby. In addition, for any register which will be driven in a forward or reverse direction, it is necessary that on the least significant digit display wheel the positive snap-action take place on the "9" when going forward and on the "0" going in reverse. With the magnetic "snap-over" system described above, the "snap-over" action takes place only at one position.
Another potential solution to the problem associated with ambiguous display readings is to increase the number of contacts on the adjacent encoder circuit board. While reducing the chance of ambiguity, with this arrangement it is still possible for an ambiguous reading to occur. In addition, this arrangement suffers from the drawback of increased drag due to friction between the wiper arm and the additional contact pads. In any register display mechanism, drag and friction should be kept to a minimum so as to not affect the accuracy of the meter reading. This is because the metering mechanisms employed are generally accurate as long as a low load or drag is present at their output to the display mechanism. High drag present in the mechanism may cause the metering mechanism to slow down and cause the display to read less than the actual amount of the quantity being measured by the metering mechanism.